Segmental instability and degenerative changes of the lumbar spine is considered a major etiology of persistent low back pain. However, the anatomic changes in the intervertebral disc, vertebral body, and facet joints associated with instability are not clearly known yet, and their relationship with pain is even more elusive. Because of the widespread nature of disc degeneration which can occur with and without segmental instability, it is essential to develop methods to diagnose this entity and to provide effective treatment, which is the long-term goal of our research. We propose a 5-year study of the in vivo relationship of degenerative changes and segmental instability of the lumbar spine. In this study, we will compare 56 asymptomatic normal volunteers and 56 age- and sex-matched symptomatic patients. Hypotheses that we will test in this study are: (1) in vivo torsional instability of the lumbar spine is greater in grade 3 or 4 (moderate or severe) degenerated discs than in normal or grade 5 (advanced) degenerated discs; (2) Degenerative changes in the facet joints and vertebral bodies are significantly correlated with torsional instability and disc degeneration; and (3) There are significant differences in these relationships between the asymptomatic volunteers? group and the symptomatic patients? group. The specific aims are: (1) To establish an in vivo relationship between segmental motion characteristics and degenerative conditions of the intervertebral disc and facet joints; and (2) To compare the in vivo relationship between motion and degenerative conditions found in asymptomatic normal volunteers with that determined in age- and sex-matched symptomatic patients. Torsional motions resulting from passive manipulation of the trunk will be measured using computed tomography (CT) based non-invasive 3-D motion analysis method that we have previously developed. Flexion-extension motions will be measured from dynamic radiographs taken in the lateral decubitus position when the subjects produce the maximum voluntary motions. Dynamic radiographs will also be used to measure any osteophytes on the vertebral bodies. Degenerative changes of the discs and facet joints will be measured using T2-weighted sagittal and proton density axial magnetic resonance (MR) images. Pain level will be evaluated using an analogue visual scale from 0 to 10, and the subjects' physical conditions, such as other disease and activity levels, will be evaluated using a Subject Information Sheet designed for patient evaluation.